arXiv subjects

A. D. Erlykin

Publications and source records attributed to A. D. Erlykin.

At least 37 records · Page 2Linked to original sources

arXiv2009

Solar activity and the mean global temperature

The variation with time from 1956-2002 of the globally averaged rate of ionization produced by cosmic rays in the atmosphere is deduced and shown to have a cyclic component of period roughly twice the 11 year solar cycle period. Long term variations in the global average surface temperature as a function of time since 1956 are found to have a similar cyclic component. The cyclic variations are also observed in the solar irradiance and in the mean daily sun spot number. The cyclic variation in the cosmic ray rate is observed to be delayed by 2-4 years relative to the temperature, the solar irradiance and daily sun spot variations suggesting that the origin of the correlation is more likely to be direct solar activity than cosmic rays. Assuming that the correlation is caused by such solar activity, we deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to this activity is $\lesssim14%$ of the observed global warming.

physics.geo-ph↗

arXiv2008

All-particle primary energy spectrum in the 3-200 PeV energy range

We present all-particle primary cosmic-ray energy spectrum in the 3-200 PeV energy range obtained by a multi-parametric event-by-event evaluation of the primary energy. The results are obtained on the basis of an expanded EAS data set detected at mountain level (700 g/cm^2) by the GAMMA experiment. The energy evaluation method has been developed using the EAS simulation with the SIBYLL interaction model taking into account the response of GAMMA detectors and reconstruction uncertainties of EAS parameters. Nearly unbiased (<5%) energy estimations regardless of a primary nuclear mass with an accuracy of about 15-10% in the 3-200 PeV energy range respectively are attained. An irregularity ('bump') in the spectrum is observed at primary energies of ~74 PeV. This bump exceeds a smooth power-law fit to the data by about 4 standard deviations. Not rejecting stochastic nature of the bump completely, we examined the systematic uncertainties of our methods and conclude that they cannot be responsible for the observed feature.

astro-ph↗

arXiv2007

Gamma Rays frim the Galactic Centre

Recent results from the HESS gamma ray telescope have shown the presence of both a diffuse, extended, flux of gamma rays above ~0.4 TeV and discrete sources in and near the Galactic Centre. Here, we put forward a possible explanation in terms of the diffusion of cosmic ray protons from a succession of supernova remnants (SNR) in the SgrA* region of the Galaxy plus a contribution from SNR in the rest of the Galactic Centre Region, to be called the Galactic Centre Ridge (GCR). Protons are favoured over electrons because the mG magnetic fields in the Region will attenuate energetic electrons severely. Prominent features are the need for 'anomalous diffusion' of the protons in the whole region and the adoption of low efficiency for SNR acceleration in the high density regions. The latter is related by us to the well-known low 'cosmic ray gradient' in the Galaxy. A corroborating feature is the close correlation of inferred cosmic ray intensity with the smoothed intensity of 5 GHZ radio radiation. We attribute this to the presence of the SNR in the GCR.

astro-ph↗

arXiv2007

Extensive Air Showers and the Physics of High Energy Interactions

Extensive Air Showers are still the only source of information on primary cosmic rays and their interactions at energies above PeV. However, this information is hidden inside the multiplicative character of the cascading process. Inspite of the great experimental and theoretical efforts the results of different studies are often ambiguous and even conflicting. These controversies can partly be referred to imperfections of our models of high energy interactions. The first part of the paper is concerned with this problem. The author thinks that the present models should be corrected to give slightly deeper penetration of the cascade into the atmosphere. In this respect the modification suggested by the QGSJET-II model seems to be the step in the right direction. The Sibyll 2.1 model provides a similar penetrating properties. However, this modification is not enough and a small additional transfer of the energy from EAS hadrons to the electromagnetic component is needed too. As a possible candidate for such a process the inelastic charge exchange of pions is discussed. In the second part of the paper the author discusses the need to account for the interaction of EAS with the stuff of detectors, their environment and the ground in the light of the 'neutron thunder' phenomenon, discovered recently.

hep-ph↗

arXiv2007

The neutron 'thunder' accompanying the extensive air shower

Simulations show that neutrons are the most abundant component among extensive air shower hadrons. However, multiple neutrons which appear with long delays in neutron monitors nearby the EAS core ('neutron thunder') are mostly not the neutrons of the shower, but have a secondary origin. The bulk of them is produced by high energy EAS hadrons hitting the monitors. The delays are due to the termalization and diffusion of neutrons in the moderator and reflector of the monitor accompanied by the production of secondary gamma-quanta. This conclusion raises the important problem of the interaction of EAS with the ground, the stuff of the detectors and their environment since they have often hydrogen containing materials like polyethilene in neutron monitors. Such interaction can give an additional contribution to the signal in the EAS detectors. It can be particularly important for the signals from scintillator or water tank detectors at km-long distances from the EAS core where neutrons of the shower become the dominant component after a few mcsec behind the EAS front.

hep-ph↗

arXiv2006

The neutron 'thunder' accompanying large extensive air showers

The bulk of neutrons which appear with long delays in neutron monitors nearby the EAS core (~'neutron thunder'~) are produced by high energy EAS hadrons hitting the monitors. This conclusion raises an important problem of the interaction of EAS with the ground, the stuff of the detectors and their environment. Such interaction can give an additional contribution to the signal in the EAS detectors at {\em km}-long distances from the large EAS core after a few $μs$ behind the EAS front.

hep-ph↗

arXiv2006

The Anatomy of the Knee and Gamma-Families

It is shown that the fine stucture of the cosmic ray energy spectrum in the knee region, if explained by the Single Source Model (SSM), can, in principle, be clearly revealed and magnified in the size spectrum of extensive air showers (EAS) associated with gamma families. Existing experimental data on EAS at mountain level give support to this hypothesis.

hep-ph↗

arXiv2006

Fine structure in the gamma-ray sky and the origin of UHECR

The EGRET results for gamma ray intensities in and near the Galactic Plane have been analysed in some detail. Attention has been concentrated on energies above 1 GeV and the individual intensities in a $4^{\circ}$ longitude bin have been determined and compared with the large scale mean found from a nine-degree polynomial fit. Comparison has been made of the observed standard deviation for the ratio of these intensities with that expected from variants of our model. The basic model adopts cosmic ray origin from supernova remnants, the particles then diffusing through the Galaxy with our usual `anomalous diffusion'. The variants involve the clustering of SN, a frequency distribution for supernova explosion energies, and 'normal', rather than 'anomalous' diffusion. It is found that for supernovae of unique energy, and our usual anomalous diffusion, clustering is necessary, particularly in the Inner Galaxy. An alternative, and preferred, situation is to adopt the model with a frequency distribution of supernova energies. The results for the Outer Galaxy are such that no clustering is required. If their explosion energies are distributed then supernovae can be the origin of UHECR.

astro-ph↗

arXiv2006

Fine structure in the gamma-ray sky

The EGRET results for gamma-ray intensities in and near the Galactic Plane have been analysed in some detail. Attention has been concentrated on energies above 1 GeV and the individual intensities in a $4^\circ$ longitude bin have been determined and compared with the large scale mean found from a nine-degree polynomial fit. Comparison has been made of the observed standard deviation for the ratio of these intensities with that expected from variants of our model. The basic model adopts cosmic ray origin from supernova remnants, the particles then diffusing through the Galaxy with our usual 'anomalous diffusion'. The variants involve the clustering of SN, a frequency distribution for supernova explosion energies, and 'normal', rather than 'anomalous' diffusion. It is found that for supernovae of unique energy, and our usual anomalous diffusion, clustering is necessary, particularly in the Inner Galaxy. An alternative, and preferred, situation is to adopt the model with a frequency distribution of supernova energies. The results for the Outer Galaxy are such that no clustering is required.

astro-ph↗

arXiv2006

The Anisotropy of Galactic Cosmic Rays as a Product of Stochastic Supernova Explosions

We study the effect of the stochastic character of supernova explosions on the anisotropy of galactic cosmic rays below the knee. We conclude that if the bulk of cosmic rays are produced in supernova explosions the observed small and nearly energy independent amplitude of the anisotropy and its phase are to the large extent determined by the history of these explosions in the vicinity of the solar system, namely by the location and the age of the supernova remnants, within a few kpc, which give the highest contribution to the total intensity at the present epoch. Among the most important factors which result in the small magnitude and the energy independence of the anisotropy amplitude are the mixed primary mass composition, the effect of the Single Source and the Galactic Halo. Special attention is given to the phase of the anisotropy. It is shown that the excessive flux from the Outer Galaxy can be due to the location of the solar system at the inner edge of the Orion Arm which has the enhanced density and rate of supernova explosions.

astro-ph↗

arXiv2005

The nature of the 'knee' in the cosmic ray energy spectrum

In view of recent developments attention is directed again at two aspects of the well known 'knee' in the cosmic ray energy spectrum at 3 PeV: the mass of the predominant particles at this energy and their source. It is inevitable in a subject such as this that ideas - and conclusions - evolve. Earlier, we had used a particular acceleration model and the nature of the local ISM to infer that the particles are mainly oxygen nuclei. Initially no specific source was identified. More recently, however, we have specified the Monogem Ring supernova remnant (SNR) as the likely source; this is at just the right distance and age and the energies are reasonable. Concerning the mass composition at the knee, a quantity more difficult to determine, recent direct measurements, which extend to higher energies than hitherto, show a likely flattening in the spectrum above 10^4 GeV/nucleon for He-nuclei, a flattening which, if extrapolated to higher energies, would meet the measured spectrum in the knee region. The other nuclei do not show this feature. He-nuclei in the knee region would also be marginally consistent with KASCADE EAS data, although there are serious problems with EAS mass estimates in that experiment. Concerning the acceleration, recent models applied to the Monogem Ring SNR allow a satisfactory explanation in terms of either oxygen or helium, but with the latter being a distinct possibility and perhaps more likely.

astro-ph↗

arXiv2005

The Origin of Cosmic Rays

It is generally regarded that the bulk of cosmic rays originate in the Galaxy and that those below the 'knee' (the rapid steepening in the energy spectrum) at a few PeV come from Galactic supernovae, the particles being accelerated by the shocks in the supernova remnants. At higher energies, there are problems in that conventional SNR - which surely constitute the bulk of the sources - have a natural limit at a few tens of PeV (for iron nuclei). The question of the origin of particles above this limit is thus an open one. Here we examine a number of possibilities: a variety of supernovae and hypernovae, pulsars, a Giant Galactic Halo and an Extragalactic origin. A relevant property of any model is the extent to which it can provide the lack of significant irregularity of the energy spectrum. Although it is appreciated that spectral measurements are subject to systematic as well as random errors we consider that contemporary data are good enough to allow at least some progress in this field. In the search for origin above PeV energies we conclude that shocks in the Galactic Halo, whatever their source (Galactic wind, relativistic plasmoids - 'cannonballs', multiple shocks from supernovae etc.) are most likely, pulsrs such as B0656+14 and hypernovae come a close second although such a suggestion is not without its difficulties. What is most important is that trapping of particles in the Halo is needed to reduce irregularities of the energy spectra both below and above the 'knee' caused by the stochastic nature of supernova explosions and other potential (discrete) Galactic sources. We argue that precise experimental studies of spectral 'irregularities' will provide considerable help in the search for cosmic ray origin.

astro-ph↗

arXiv2005

Comparison between methods for the determination of the primary cosmic ray mass composition from the longitudinal profile of atmospheric cascades

The determination of the primary cosmic ray mass composition from the longitudinal development of atmospheric cascades is still a debated issue. In this work we discuss several data analysis methods and show that if the entire information contained in the longitudinal profile is exploited, reliable results may be obtained. Among the proposed methods FCC ('Fit of the Cascade Curve'), MTA ('Multiparametric Topological Analysis') and NNA ('Neural Net Analysis') with conjugate gradient optimization algorithm give the best accuracy.

astro-ph↗

arXiv2005

'Sling effect' in the development of atmospheric cascades induced by primary cosmic ray nuclei

The 'Sling effect' appears when a fragment of a projectile nucleus emitted after its peripheral collision with a target nucleus is caused to rotate with a high spin. The spinning fragment has a deformed shape and looks like an oblate ellipsoid. Due to the virtual non-compressibility of nuclear matter, and the polarization of the spin in the plane transverse to the input momentum of the projectile nucleus such an ellipsoid has a reduced mean interaction cross-section compared with a non-spinning fragment which has a spherical shape. Purely geometrical arguments dictate that such an ellipsoidal nucleus should have additional fluctuations of cross-section even at a fixed impact parameter dependent on the orientation angle between the axis of the ellipsoid and the vector connecting the centers of projectile and target nucleus. The number of 'wounded nucleons' in the projectile nucleus participating in the interaction correlates strongly with the interaction cross-section. All these effects lead to a non-exponential attenuation of fragments and increased probability for a fragment to penetrate down to a larger depth in the absorber, than normal. If the sling effect appears in the interaction of a primary cosmic ray nucleus with nuclei in the atmosphere the induced atmospheric cascade will have a slower attenuation, and thereby can help to reduce some important inconsistencies in the interpretation of the existing experimental data on extensive air showers, observed in the lower half of the atmosphere. The paperr gives numerical estimates of the sling effect.

astro-ph↗

arXiv2004

Models and phenomenology

It is evident that models of the knee should match the observational phenomenology. In this talk I discuss a few aspects of phenomenology, which are important not only for the understanding of the knee origin, but also for the general problem of the origin of cosmic rays. Among them are the shape of the energy spectrum, its irregularity, the sharpness of the knee and its fine structure. The classification of models is given and some examples of the most recent models are discussed. The most probable conclusion deduced from this examination is that the knee has an astrophysical origin and the so called 'source' models of the knee are most likely among them.

astro-ph↗

arXiv2004

A new method for the UHECR mass composition studies

The detemination of the primary cosmic ray mass composition from the longitudinal development of atmospheric cascades is still an open problem. In this work we propose a new method of the multiparametric topological analysis and show that if both X$_{max}$ - the depth of shower maximum and N$_{max}$ - the number of charged particles in the shower maximum are used, reliable results can be obtained.

astro-ph↗

arXiv2004

A new multiparametric topological method for determining the primary cosmic ray mass composition in the knee energy region

The determination of the primary cosmic ray mass composition from the characteristics of extensive air showers (EAS), obtained at an observation level in the lower half of the atmosphere, is still an open problem. In this work we propose a new method of the Multiparametric Topological Analysis and show its applicability for the determination of the mass composition of the primary cosmic rays at the PeV energy region.

astro-ph↗

arXiv2004

Are there pulsars in the knee ?

Recent findings indicate that the Monogem Ring supernova remnant and the associated pulsar PSR B0656+14 may be the 'Single Source' responsible for the formation of the sharp knee in the cosmic ray energy spectrum at $\sim$3PeV. We estimate the contribution of the pulsar B0656+14 to the cosmic rays in the PeV region and conclude that the pulsar cannot contribute more than 15% to the cosmic ray intensity at the knee. Therefore it cannot be the dominant source there and an SNR is still needed. We also examine the possibility of the pulsar giving the peak of the extensive air shower intensity observed from the region inside the Monogem Ring. The estimates of the gamma-ray flux produced by cosmic ray particles from this pulsar indicate that it can be the source of the observed peak, if the particles were confined within the SNR during a considerable fraction of its total age. We also estimate the contribution of Geminga and Vela pulsars to cosmic rays at the knee.

astro-ph↗